Abstract

This paper presents the details of preliminary studies relating to introducing advanced light weight truss based structural concepts in civil aircraft structures. A typical civil aircraft horizontal tail (HT) segment has been considered. The proposed composite structure is an unconventional structure with Iso-truss T-section spar, rib and orthogonal grid skin replacing the conventional full web, and thicker skin. The truss elements are made out of polyurethane foam and glass braids. Wet layup technique is used for the truss element, T-section and skin. The epoxy resin 5052 system is used. Both the main loading members (rib and spar) are made of the truss elements. The role of the skin is mainly to give an aerodynamic shape and transfer the load to the sub structure comprising of truss elements. The skin buckling is avoided by introducing the orthogonal grid. A GFRP truss based segment of HT has been designed, analyzed, fabricated and tested. The overall dimension of the fabricated segment is 780 *1260*192mm. Tensile tests have been carried out on Bi-directional GRFP (0/90) laminates and elemental truss elements for obtaining the material properties. A static test has been carried out on truss structure for Gust case which is the critical load case. The full load acting on the segment is 636 Kg. The GFRP segment is loaded up to 30% of full load (191 Kg). For this load of 191 kg the maximum deflection of 14.28 mm was observed. The deflections are monitored at the end rib and compared with the NASTRAN FE model. The correlation between analysis and testing is good. The truss based construction improves the stiffness of the structure and weight saving compared to the conventional method of fabrication. This paper details the design, analysis and fabrication of the truss based concepts on the HT segment.